1. Field of the Invention
The present invention relates to alkylation. In another aspect, the present invention relates to the alkylation of olefins utilizing isoparaffins. In still another aspect, the present invention relates to the alkylation of C.sub.3 to C.sub.5 olefins utilizing a mixture of C.sub.4 and C.sub.5 isoparaffins. In yet another aspect, the present invention relates to the alkylation of C.sub.3 to C.sub.5 olefins utilizing a suitable mixture of C.sub.4 and C.sub.5 isoparaffins to increase alkylation yield. In still yet another aspect, the present invention relates to the alkylation of C.sub.3 to C.sub.5 olefins utilizing a suitable mixture of C.sub.4 and C.sub.5 isoparaffins to produce a resulting alkylation product having an improved Reid Vapor Pressure ("RVP").
2. Description of the Related Art
Alkylation is a well known refinery process for converting light gaseous olefins into high-octane gasoline components.
As practiced commercially, alkylation generally involves reacting isobutane with C.sub.3 to C.sub.5 olefins in the presence of an acid catalyst, typically either hydrofluoric acid or sulfuric acid. The resulting alkylate product comprises predominately C.sub.7 to C.sub.9 isoparaffins, along with lesser amounts of lighter and heavier isoparaffins in the C.sub.6 to C.sub.12 range, and some isopentane.
Recent reformulated gasoline specifications require a reduction in both the Reid Vapor Pressure ("RVP") and the olefin content. Alkylate is a low vapor pressure, high octane gasoline blending component containing no olefins. Thus, it helps refiners meet the new reduced RVP and reduced olefin content specifications. Additionally, alkylate burns cleanly, resulting in lower levels of undesired emisisons from gasoline engines.
U.S. Pat. No. 2,347,317, issued Apr. 25, 1944 to Gibson, discloses a process for converting relatively low-boiling hydrocarbons to motor fuel hydrocarbons in the presence of hydrofluoric acid. As disclosed, the process of U.S. Pat. No. 2,347,317 generally involves reacting a mixture of isobutane, normal butane, and hydrofluoric acid in excess of that required to form an azeotropic mixture with the isobutane. Distillation of the resulting product produces an overhead distillate mixture of hydrofluoric acid and isobutane, which is then cooled and separated into a hydrofluoric liquid phase and an isobutane liquid phase. The process of U.S. Pat. No. 2,347,317 is also disclosed as being especially advantageous in a combination isomerization-alkylation process in which normal butane is isomerized to isobutane in the presence of hydrofluoric acid. Gibson does disclose that in isomerizing normal pentane, isobutane is generally also produced, and that the combined isobutane and isopentane may be subjected to alkylation. However, Gibson does not disclose or teach that the production of isopentane can be controlled by varying the ratio of isobutane to isopentane, that the yield of the alkylation can be controlled by varying the ratio of isobutane to isopentane, or that the RVP of the alkylated product can be controlled by varying the ratio of isobutane to isopentane.
U.S. Pat. No. 2,405,993, issued Aug. 20, 1946 to Burk discloses the alkylation of higher molecular weight hydrocarbons with isopentane, and that alkylation with isopentane results in the production of isobutane. Burk further discloses that isopentane or mixtures of isopentane and isobutane may be reacted with hydrocarbons of more than five carbon atoms such that products in the gasoline range are obtained. However, Burk does not disclose or teach that production of isopentane can be controlled by varying the ratio of isobutane to isopentane, that the yield of the alkylation can be controlled by varying the ratio of isobutane to isopentane, or that the RVP of the alkylated product can be controlled by varying the ratio of isobutane to isopentane.
U.S. Pat. No. 2,509,028, issued May 23, 1950 to Abrams et al. discloses a method of producing gasoline by alkylation in which an entire alkylation reaction mixture containing hydrofluoric acid catalyst is introduced into a fractionating unit. In the unit the isoparaffins are reformed by further contact with the hydrogen fluoride catalyst under conditions which maintain material of the gasoline-boiling range and higher in liquid form, while lighter material, including hydrogen fluoride, vaporizes. Abrams et al. do not disclose or teach that production of isopentane can be controlled by varying the ratio of isobutane to isopentane, that the yield of the alkylation can be controlled by varying the ratio of isobutane to isopentane, or that the RVP of the alkylated product can be controlled by varying the ratio of isobutane to isopentane.
U.S. Pat. No. 3,045,055, issued Jul. 17, 1960 to Van Pool et al. generally discloses a process for the alkylation of a isoparaffin and the reforming of a hydrocarbon wherein each operation is arranged to benefit the other. Specifically, the process as disclosed by Van Pool et al. generally includes alkylation of an isoparaffin and an olefin in the presence of a hydrogen fluoride catalyst to obtain an alkylate effluent comprising an alkylate product, organic fluorides and normal paraffin. Van Pool et al. disclose that the charge materials introduced into the alkylation zone may include propylene, butylenes, amylenes, isobutane, isopentane, propyl fluorides, butyl fluorides, and amyl fluorides. Van Pool et al. further disclose that the preferred alkylation charge is an olefin-isoparaffin, preferably butylenes-isobutane. Van Pool et al. do not disclose or teach that production of isopentane can be controlled by varying the ratio of isobutane to isopentane, that the yield of the alkylation can be controlled by varying the ratio of isobutane to isopentane, or that the RVP of the alkylated product can be controlled by varying the ratio of isobutane to isopentane.
U.S. Pat. No. 3,211,803, issued Oct. 12, 1965 to Chapman discloses an alkylation process for the elimination of heavy alkylate utilizing both alkylation and reforming. Chapman does not disclose or teach that production of isopentane can be controlled by varying the ratio of isobutane to isopentane, that the yield of the alkylation can be controlled by varying the ratio of isobutane to isopentane, or that the RVP of the alkylated product can be controlled by varying the ratio of isobutane to isopentane.
U.S. Pat. No. 3,502,569, issued Mar. 24, 1970 to Hervert discloses a process for the production of high octane motor fuel by alkylation and reforming. Hervert discloses that alkylation may be carried out by the catalytic alkylation of isobutane and/or isopentane with propylenes, butylenes and amylenes. Specifically Hervert discloses alkylating isobutane with C.sub.4 mono-olefin in the presence of an acid catalyst to produce an alkylate product containing dimethylhexanes. This alkylate is then separated into various fractions based on octane content. The lower-octane fraction is then reformed by admixture with hydrogen and a reforming catalyst. Finally, a portion of the reformate is commingled with the high-octane alkylate fraction to produce a suitable motor fuel alkylate. Hervert does not disclose or teach that production of isopentane can be controlled by varying the ratio of isobutane to isopentane, that the yield of the alkylation can be controlled by varying the ratio of isobutane to isopentane, or that the RVP of the alkylated product can be controlled by varying the ratio of isobutane to isopentane.
Recent patents also generally disclose the use of mixtures of isoparaffins. See U.S. Pat. No. 4,225,740, at col. 3, lines 11-16; U.S. Pat. No. 4,276,439, at col. 2, lines 14-18; and U.S. Pat. No. 4,513,165 at col. 2, lines 39-41. Like the above cited patents, these recent patents also do not disclose or teach that production of isopentane can be controlled by varying the ratio of isobutane to isopentane, that the yield of the alkylation can be controlled by varying the ratio of isobutane to isopentane, or that the RVP of the alkylated product can be controlled by varying the ratio of isobutane to isopentane.
As recent reformulated gasoline specifications require a reduction in the Reid Vapor Pressure ("RVP") and a reduction in the olefin content, there is a need in the art for an alkylation process that will produce alkylate that has a lowered RVP and that will help lower the olefin content of the gasoline pool.
As production of C.sub.5 paraffins increases its presence in the final gasoline pool and thus negatively effects the desired or target RVP and resultant yield, there is a need in the art for an alkylation process that will reduce, eliminate or control the production of C.sub.5 paraffins in the alkylation process.
Other needs of the art will become evident to those of skill in the alkylation art upon reading this specification.